Various devices and machines generate heat, such as chemical heat generation due to burning and reaction etc. and electrical heat generation (Joule heat generation) caused by current flow in a circuit. In order for such devices and machines to be stably operated, efficient thermal conduction may be required from the high-temperature side to the low-temperature side without heat accumulation. In addition, a thermal stress is generated depending on the temperature difference (or temperature gradient) and the difference in coefficient of expansion among respective physical bodies that constitute such devices and machines (e.g., a high-temperature substance and a low-temperature substance, and each physical body located therebetween). To enhance the durability and reliability of devices and machines, such a thermal stress may also have to be reduced or relaxed among them (e.g., a high-temperature substance and a low-temperature substance, and each physical body located therebetween).
To this end, a thermal conductive stress relaxation structure can be interposed between the high-temperature substance and the low-temperature substance so as to be able to satisfy both the thermal conductivity and the thermal stress relaxation ability. Descriptions relevant to such a thermal conductive stress relaxation structure are disclosed in each Patent Literature (PTL) below, for example.